1. Field of the Invention
The present invention relates to a method for desulfurizing a molten iron by injection particularly by using calcium carbonate which has been heretofore considered to be low in the desulfurizing ability or to lower said function as a desulfurizing agent. The term "desulfurization by injection" is expressed by "injection-desulfurization" hereinafter.
2. Description of the Prior Art
Prior desulfurizing agents used in the injection- desulfurization of a molten iron are mainly calcium carbide or quicklime (CaO). Among them, calcium carbide has been most broadly used because of a high reaction efficiency and a small used amount. However, calcium carbide is usually produced by reacting mixture of quicklime and coke in an electric furnace, so that calcium carbide is high in cost and therefore, a desulfurizing agent consisting mainly of quicklime has been recently used instead of calcium carbide.
In the injection-desulfurization using a carrier gas, when powdery calcium carbide or quicklime is used, it is necessary to mix a small amount of calcium carbonate or other gas-forming substances in order to promote the stirring of the molten bath. However, calcium in calcium carbonate has been considered to be an ingredient which does not serve to the desulfurizing reaction, because this compound is decomposed to form CO.sub.2 and the reaction site becomes an oxidizing atmosphere and therefore calcium carbonate is only used as a desulfurizing aid, and the used amount is limited to the necessary lowest amount. Accordingly, it has never been intended to use calcium carbonate alone as the main active ingredient.